One of the first problems a capacitive-sensor analog designer must face is the low-frequency cutoff. Theoretically, you must fulfill just one simple requirement: a sufficiently large input resistance of the preamplifier's first stage...
Articles and news - 9
Solve low-frequency-cutoff problems in capacitive sensors
Introduction to linear variable differential transformers (LVDTs)
The linear variable differential transformer (LVDT) is an electromechanical transducer that senses the mechanical displacement of a core and produces a proportional AC voltage at the output...
Sine reference is synchronous with ac line
Many applications require a sinusoidal reference voltage synchronized to the ac line voltage. You cannot derive such a reference voltage directly from the ac line because the waveform of the ac line is distorted...
Laser simulator helps avoid destroyed diodes
Laser diodes can destroy themselves in a few nanoseconds, so testing the response and stability of a feedback-stabilized laser-diode driver can be expensive...
Light powers isolation amplifier
Self-powered isolation amplifiers, which need no external isolated power supply, provide versatile and convenient interfaces in many applications that require galvanic isolation of the signal source...
Input-protection scheme tops other approaches
You typically accomplish overvoltage or surge protection at circuit inputs by connecting diodes to the supply rails, connecting zener diodes to ground, or connecting transzorbs to ground. Unfortunately, for high-energy surges at the inputs, connecting diodes to the supply rails results in surges in supply lines...
Clamping circuit dissipates minimal power
The circuit is a quasi-linear regulator. It functions as a source follower for input voltages greater than a preset level, determined by VR3. For input voltages lower than the preset level, the pass element, Q2, operates as a saturated switch...
Classic 3-leg adjustable regulators have a shunt mode? Who knew?
When parts have been around as long, and in such widespread use, as the venerable LM317 and LM337 (and their siblings), you tend to think every trick that can be played with them is already in the (data)book...
Light a white LED from half a cell
White LEDs are rapidly gaining popularity as sources of illumination, as in LCD backlights, but with forward voltages typically ranging from 3 to 5 V, operating them from a single cell presents obvious difficulties...
LED driver delivers constant luminosity
The circuit is similar in principle to that of a previous Design Idea but offers improved, more reproducible performance. The output current is almost constant over an input-voltage range of 1.2 to 1.5 V and is insensitive to variations of transistor gain...
